This invention relates to a method of producing a package by forming a pouch in a first foil thereby stretching the material, putting the commodity to be packed into the space between this pouch and a second foil, sealing both foils together and shrinking the first foil in the area of the pouch by applying heat.
German Patent Publication DT-AS 1 145 087 discloses this method. By forming the pouch at a temperature below the softening point of the thermoplastic material a stretching is effected which makes the foil in the region of the pouch shrinkable thus effecting a complete or approximate restoration of the original plane shape by the application of heat.
In this publication (DT-AS 1 145 087) an evacuation of the package is not proposed.
It has also been proposed (U.S. Pat. No. 2,376,583) to cover the product to be packed by a foil which has been stretched on the whole. This foil is then fixed with a clamp and the air contained inside is evacuated to a certain extent. Finally the foil is shrunk by applying heat to eliminate wrinkles which may be caused by the atmospheric pressure.
In this last mentioned method the shrinking force is often insufficient to remove the wrinkles which are caused by the atmospheric pressure upon the evacuated package.
An apparatus for producing packages comprising a molding station, a filling station, and an evacuation and sealing station is described in the DT-AS 23 23 409.